CONTRIBUTIONS TO THE GEOLOGY OF BENGUELLA. 511 



from Lepi to Calenga, after leaving Homer's Camp, ascends over weathered gray- 

 wacke and reaches the plateau near a 60-foot kopje of subquartzitic grit, which 

 weathers gray and consists of grains of about one -eighth inch in diameter. 



Further along the line at km. 387 the white weathered banded cherts are covered 

 by a yellow soil. One and a half kilometres further east a view down the upper 

 valley of the Calai, the head stream of the Cunene, is bounded to the east by a long 

 regular escarpment of the Calenga quartzite, which dips 10° eastward. East of 

 Calenga the granitic rocks soon reappear from beneath the Lepi graywackes, and 

 picturesque tors are seen in the distance ; but the sedimentary series continues along 

 the high ground to km. 395. Blue-hearted cherty graywackes are exposed beside 

 the railway at km. 391, and at km. 392^ is a dyke of coarse dark-blue epidiorite. 



Just east of the locality known as Varian's Camp, at km. 393, is a deep gully, 

 which exposes the blue cherty graywackes. They are somewhat coarser in grain 

 than those near Lepi, and hand specimens that show large fragments of felspar 

 resemble porphyritic felsites ; the rock contains pyrites, secondary quartz, and 

 granules of epidote, but it lacks the incipient foliation of the epidotic quartzite 

 (No. 135). The railway cuttings on the eastern side of this ravine, at about 

 km. 394^, are of sandstone interbedded with slate and graywacke and dipping 15° 

 eastward. From this point there is a long tract of level ground with no sections. 

 Bold tors to the north and south indicate that the lower ground on both sides of the 

 ridge followed by the railway consists of granite. The ridge itself is probably capped 

 by a thin layer of the graywackes, as just before reaching the Kunhungamua bridge 

 the ground is littered with felspathic graywacke, but I could see none in situ. 

 Immediately to the east of the railway bridge is a hill of porphyritic granite. The 

 rock has a compact, fine-grained selvage which, as Mr Tyrrell has shown, contains 

 cassiterite. After leaving these granite exposures we saw no rock in situ before 

 reaching " Huambo Crossing," 5 km. further east. The railway cuttings are in buff 

 rock-sand, which might be formed either from decomposed granite or from dis- 

 integrated arkose. From Huambo Crossing, which is on granite, we could see 

 granite tors both north beyond Huambo Fort and southward, bearing 147°, in the 

 valley of the Cunene. 



E. Huambo to Ochilesa. 



From Mount Salioa, near the head of the Lengwe Gorge, to Huambo, and, as we 

 found later, extending 25 miles further east to Candumbo, is a long belt of granite, 

 which is only hidden from view where it is covered by the sandstones and rhyolites 

 of the Oendolongo Mountains and by the graywackes and quartzites of the Serra 

 Corvo Andrade between Lepi and Kunhungamua. These sedimentary rocks are 

 mainly composed of the waste of the underlying granites, so they give rise to soils 

 of similar quality which are of only second-rate value. The uniformity of the 

 conditions was probably clue to our route having followed along the grain of the 



TRANS. ROY. SOC. EDIN., VOL. LI, PART III (NO. 13). 74 



